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Posted: 10/22/2004 5:30:55 PM EDT
There has been much discussion over the military's use of chrome plated bolts and carriers in the past. There have been many theories and speculation as to why their use was discontinued. These range from the chrome flaking or wearing off and somehow becoming imbedded into the upper receiver, to the hardness of the chrome carrier itself, both contributing to accelerated wear of the upper receiver. Some claim that these components are brittle and more prone to failure due to the plating process. I believe that most of these commonly held misconceptions revolve around people misinterpreting the intent of the inspection criteria that has been published in the various Technical Manuals printed over the years. The result of these assumptions, combined with failures related to surplus parts that are approaching 40 years of age along with commercially produced parts which are notorious for being substandard, have somehow made all of this theory and speculation internet “fact”. When someone disagrees with this “fact” they are quickly made aware of it’s existence, politely or otherwise by the various experts who can only regurgitate the same information with no supporting documentation.

So, in an effort to not be accused of trolling, I am offering my experience on this subject in how the maintenance system works in an attempt to try and reduce some of the misinformation and the resulting pissing contest relating to this issue. I for one know the documentation quest can be a double edged sword, as there is rarely a smoking gun that can easily answer complicated questions with a simple yes or no. I have spent a fair amount of my time making inquiries and researching the resources I have available to me and still have not found definitive answers to some technical and historical questions relating to the M16 and this topic in particular. In the absence of documentation to support some of these misguided theories we must rely on the available documentation with an understanding of how the military maintenance system works in order to draw an educated conclusion.

The paragraph contained in any era of the TM(Technical Manual) or TB(Technical Bulletin) since about 1972 in any of it’s minor versions including the current TM that covers the A2, A4 and M4 variants that leads to most of this confusion and misinterpretation states:

“There are bolts and bolt carriers on fielded rifles, some with chrome plated exterior surface finishes and some with phosphate coating. Both finishes are acceptable under certain operational requirements and/or restrictions. Phosphate coated bolt carriers are required for divisional combat units. Chrome plated bolt carriers are acceptable for divisional non-combat units and training center units. Chrome plated and phosphate coated bolt assemblies, bolt carrier assemblies, and repair parts for these assemblies may be intermixed in any combination, with the following exception:

Phosphate coated bolt carriers are required for all deployable and deploying units. Chrome plated bolt carriers are acceptable for non-deployable and training center units.”

In the 20 plus years I’ve worked within the system I have never seen one(1) MAM(Maintenance Advisory Message), SOUM(Safety Of Use Message) or even an MWO(Modification Work Order) that addressed the discontinued use of chrome bolt carriers due to a maintenance or safety related issue. Regardless of the era when any of these messages “may” have been published they would still be readily available or their existence confirmed with a little research. As is the same for any system still within the inventory. I have yet to find such a message.

The contention that they would somehow be acceptable for training or CONUS(Continental U.S.) use if they were in fact a safety or maintenance issue is absurd. The U.S. military takes the safety it’s personnel and the operational readiness of it’s equipment very seriously. Any part/component suspected of degrading either, is documented and entirely purged from the system via one of the previously mentioned message types. Even when only a small percentage of the pieces in question are found to be defective. The recent Emco barrel fiasco is a good example of this policy. Once the problem with these barrels surfaced, within a relatively short period of time any weapon having one was identified for a replacement. All this for a non-safety related malfunction found in approximately 5% or less of the rifles with these barrels. If the theory of the plating process reducing the strength or increasing the brittleness of the parts held true, then chrome bolts should suffer a greater rate of failure. This would result in military policy/doctrine completely removing them from the system. Yet, even to this day chrome bolts are acceptable, even in Divisional units. Though rarely encountered these days, I have not seen a chrome bolt that failed headspace or that broke at the cam pin hole or was otherwise unserviceable. Unlike their commercial counterparts. So I think we can put the accelerated wear, malfunctions or safety Theory to rest.

Some will argue that the chrome carrier reflecting light theory was not a valid reason to discontinue use of the chrome carrier as we are trained to always close the ejection port cover. While that may be true by today’s training doctrine, it may not have been the case when the system was first fielded. The same can be said for proper cleaning supplies and training, they evolved with the weapon based on combat usage. This theory does have merit, as I have seen/replaced to many port covers that had become unserviceable due to being bent between the upper and lower receivers by operators during reassembly. The old style port covers were very susceptible to this damage, that’s why we have the new style port covers. This was especially evident on early AR15’s that didn’t have the take down spring reinforcement on the side of the receiver. Early M16’s and XM16E1’s also had this early port cover and suffered the same damage though not as regularly. All three of these models used chromed carriers. So, it was a common occurrence for early rifles with chrome carriers to have an unserviceable port cover resulting in an exposed chrome carrier. Through the evolution of the weapon, when the M16A1 was adopted phosphated carriers had become the spec. Functionally the only part of the carrier that needed chrome plating was the inside. The M16A1 still utilized the old style port cover though.

This leads to the only reasonable conclusion that it is, in fact what the vaguely written and often misinterpreted passages of the inspection criteria in the various TM’s and pre-embarkation standards of the TB’s have always eluded to. It is an “operational” requirement (read that as tactical), NOT to be confused with “operation” as it relates to the functioning of the weapon itself. Basically an attempt to reduce the chance of anything on the weapon that could reflect light or “shine” becoming a liability to a front line troop that alternately would not be considered a liability for training.

The standards set forth in the TM and TB for acceptable over-all finish of the weapon for Divisional combat and rapid deployment units as opposed to Training and CONUS units also supports this reasoning. The amount of SFL(Solid Film Lubricant) authorized for touching up the finish of a weapon is also different for Divisional as opposed to Training/CONUS units further supports this. So it is all boils down to a matter of finish. The more finish on a front line rifle the better. The less shine, the less likelihood of becoming a tactical liability. More importantly though is that front line troops use their weapons more and they are more exposed to the elements. So they are more likely to develop corrosion that could render them unserviceable. Weapons that start life in the field with all or most of their protective finishes usually live longer than those that don’t. But in the instance of the chrome carrier it’s corrosion resistance does not outweigh it’s potential liability.

Wpns Man
Link Posted: 10/22/2004 11:48:57 PM EDT
Link Posted: 10/23/2004 5:10:14 AM EDT
Link Posted: 10/23/2004 6:45:41 AM EDT
[Last Edit: 10/29/2004 4:12:00 PM EDT by WpnsMan]

With all due respect, I am NOT trying to flame you personally but, this is the undocumented speculation and conjecture I was referring to that is so often stated as "fact".

I agree that in the '68-'69 time frame most of the new rifles being shipped had phosphated bolt carriers as that had become the spec and follows the evolution of the weapon. But, I have never been able to find any documentation that states the reason for replacing chrome carriers was due to the chrome flaking off or anything else of that nature. If that had been the case then there would surely have been a message relating to this defect along with instructions pertaining to the identification and replacement of them. As I tried to convey in my original post, if chrome carriers were in fact somehow defective they would NOT be allowed to remain in the system for CONUS units, training centers, the NG or the Reserves. That is how the maintenance system works.

In the absence of any messages stating this, it would have been a simple matter to change the inspection criteria via the next TM Change to reflect the discontinued use and removal of chrome carriers or bolts from the inventory if they had been linked to the functioning or safe operation of the weapon. I have about evey TM pertaining to the M16 starting in Aug 1966(XM16E1) to the current edition, including all of the Changes and none of them make reference to this. If it had been the case then these carriers and bolts would have been gone within a two year period. It would not have been necessary to track them down, as they would have been identified in the course of Annual Gaging by Direct Support. Gaging is accomplished every year in the Active Component and a minimum of every two years in the Guard and Reserves.

The TM and TB inspection criteria did change to state that: "Phosphate coated bolt carriers are required for all deployable and deploying units". I think this statement is what leads people to make assumptions that it must be related to a "problem" with the chrome carriers and not for the reasoning I've already stated.

Chrome carriers are rarely found today as they are taken out of service when a weapon is turned in to Depot level maintenance for refinishing, rebuilding or upgrading to a newer type. The Depot replaces them with phosphated carriers as they rarely know the final destination or type of unit the weapon will end up at. In this day and age everyone is deployable, so it makes sense. Chrome bolts on the other hand do show up occasionally though rarely these days. The ones I encounter are usually in A1's that were rebuilt in the late '70's or the'80's.

I am not trying to start another pissing contest on this subject and will not engage in one. On the contrary I would like to conduct an educated discussion and more importantly share information, preferably documented in which to draw conclusions from. In an attempt to further the knowledge of myself and the members of this forum and cut through the legends and BS. I am open minded concerning this issue, it's just that the evidence to this point does not support the legend. So, if anyone can provide documentation in the form of a SOUM, MAM, MWO, Maintenance Bulletin, Etc. pertaining to this subject, or give me a lead to the same I'd appreciate it. As this is what makes this forum such a great resource.

Wpns Man

Link Posted: 10/23/2004 3:57:32 PM EDT
if i read this correctly, the only inference at this time re: the govt switchover to phosphated bolts is that there appears to be no problems w/ chromed bolts (since no tb came out stating such), but that they were being phased out after routine rebuild/inspections etc.
this makes sense to me. i believe (and its only a belief) that the chrome plating was not necessary and more expensive, so then it was dropped as a requirement either at the mfg'r or procurement level in 1967 or so. i notice that feb 1967 is stated in TBR s the date that the m16a1 was standardized, and that probably the official spec was phosphated bolts at that time. this seems to match the observations of some, that chrome bolts were found in the orig air force m16 rifles, and some of the xm16e1 rifles (at least those mfg before 2/67?). seems to me that the chrome plating was a legacy from the orig ar10 design, and that it simply was not needed when the a1 was adopted and was gradually phased out. the fact that chrome was specified in the tm/tb as for non-deployed unit rifles to me appears to be std military practice to keep the latest and current "spec'd" equipment for front line units, and older obsolete (though still usable equipment) for stateside units to serve out their useful lives until replacement......kinda like when front line units get m4/m16a2 and ng and reserve units have the m16a1?
i myself have never had a problem with flaking chrome on military bolts, and i notice no unusual wear on my uppers from their use.....
interesting info weapnsman....
Link Posted: 10/23/2004 7:05:40 PM EDT
Great information and thank you for taking the time to post it. I just bought two NIB M16 HC bolts and carriers and one thing is very noticable, they are much smoother while cycling by hand. I like them a lot and plan on buying a few more. Since none of my rifles are FA (yes the carriers have been modified according to ATFE standards, but let's not go there again) they are not going to see hard service.
Link Posted: 10/23/2004 7:26:26 PM EDT
FWIW, i have a HC in a m16, and a cut unit in my competition ar, neither has ever shown signs of
flaking etc, i also have an ar-18, with a chrome bolt, many many rounds thru both the ar18 and m16, (to the point of melting a shortie gas tube once) and never a problem with the carrier
i am glad to see wpnsman set this straight....
Link Posted: 10/24/2004 6:16:10 AM EDT

My point exactly, the change over was due to the evolution of the design. I.E. fully chroming the carrier was not functionally needed and tactically not wanted, nothing more nothing less.

Big-Bore, rlc,


I have run a chromed military carrier in one of my AR's, a XM177E2 clone for years and have not noticed any unusual wear to my upper. The carrier was used when I got it and shows hardly any noticeable wear on the rails or key after extensive use. It also has that smooth feel to it when cycling the bolt. I also milled it to more ATF friendly specs and there is No evidence of the chrome flaking where it was cut through. I also run early chromed bolts in most of my AR's as they are pretty much indestructible. They can be identified by an MP lightly etched into them. I buy them whenever I can find them.

As I stated earlier, I have never seen a military chrome carrier flake or a chrome bolt that failed headspace or cracked at the cam pin hole. I wouldn't say the same for any commercially manufactured chrome bolt though. They seem to suffer from the "embrittleness" theory and fail quite often. I think it's more of a problem with the manufacturing, materiels or heat treatment of the bolt before it gets plated though. Since in my experience, unplated commercial bolts fail at about the same rate. I am a firm believer in using only GI, Colt or FN bolts in anything other than a range gun.

Wpns Man
Link Posted: 10/24/2004 6:25:56 AM EDT
[Last Edit: 10/24/2004 6:26:46 AM EDT by shamayim]

Originally Posted By rlc:
FWIW, i have a HC in a m16, and a cut unit in my competition ar, neither has ever shown signs of
flaking etc, i also have an ar-18, with a chrome bolt, many many rounds thru both the ar18 and m16, (to the point of melting a shortie gas tube once) and never a problem with the carrier
i am glad to see wpnsman set this straight....

Hmmmmm. Then maybe you can explain the early GI carrier key in my parts box, with significant wear on the chrome plating, down to the bare metal, on the sides.. As I recall, the carrier I pulled it off of also was showing signs of chrome loss at the edges of the bearing surfaces.

Sure do wonder where that worn off chrome went
Link Posted: 10/24/2004 8:25:02 AM EDT
[Last Edit: 10/24/2004 8:33:39 AM EDT by WpnsMan]

I recall you posting on your carrier key in the past. I assume you acquired this part as most of us do, as a used piece from some surplus or parts dealer. That being said, it is extremely hard to know the past of this part or who had their hands on it before you got it. Knowing that, I will offer some viable explanations as to how it may have arrived in it's current state.

1) It may be due to nothing more than honest though excessive wear. As you stated it has worn through to the base metal, with no mention of flaking. If so, this was probably a gradual process wherein the microscopic amounts of chrome would more than likely be suspended in the lubricant during firing and wiped out upon cleaning and re-lubricating the weapon. Unless we had the upper it came out of to inspect, I wouldn't say that it was necessarily imbedded into the upper. Not knowing the use or maintenance history of the rifle in question anything would be pure speculation. Though I'd bet it was probably worn out if it had been used enough to do that to a chromed carrier. And it would be pure speculation to infer that the chrome carrier itself was the reason for the accelerated wear. I am not trying to infer that chromed carriers or bolts do not wear out. What I am saying is that anything given enough use can and will wear out including hard chrome. We have hard chrome lined bores and I replace them all the time because the throat has worn out beyond acceptable standards.

2) It is entirely possible that it may have been stoned or filed sometime in it's life in an attempt to fit it into an upper receiver. I have had to do this numerous times at work when the upper was tight either due to damage, moron assembly or had been re-finished. The finish applied on a lot of rebuilt rifles during the late '70's to early '80's had a rough texture almost like a fine krinkle paint. This was due to either being heavily blasted before refinish or from the finish itself, that appears to be of the spray/bake on variety. The results of which are a tight fitting charging handle/carrier key track in the upper and the resulting need to occasionally stone the carrier key.

3) If the key was not sitting squarely in its recess on the carrier when it was staked, it may have ended up sittng slightly canted. If not excessively so, this would also require it to be stoned to work smoothly in an upper. Or it may have been slightly oversized and again required stoning to fit. Although I have not witnessed this on a chrome key, it is a common occurrence with many of the current phosphated replacement parts. So it remains a possibility.

4) It may have been subject to any of the above by god only knows after it left uncle's inventory and before you acquired it.

5) It may in fact be due to some anomaly in the plating process, though I suspect that it would have flaked off first if that were the case. In my experience over the years, I have probably encountered 75 to 100 chromed bolt carrier assemblies and a couple hundred chromed bolts that were still in service, and in heavily used rifles. None of them showed any sign of abnormal wear or flaking of the chrome, or abnormally high wear to the upper receiver as compared to rifles with phosphated carriers. Though not a huge pool to draw conclusions from when compared to the thousands that were manufactured, it is a broader sampling than one unserviceable carrier key with an unknown history.

Wpns Man

Link Posted: 10/24/2004 9:01:06 AM EDT
What MOS are / were you? 45 series?
I have seen a message relating to the chrome bolts and carriers and it stated rifles that were CONUS were alright with the chrome bolts and carriers but rifles that were OCONUS (overseas) had to have the chrome bolts and carriers replaced. I wish I had a copy of it! Not all of the changes that come down make it to a TM (Technical Manual). Most of the messages I have seen related to small arms never make it to the TMs. Most changes dealing with small arms go straight to direct support personal who fix the problems immediately. All small arms weapons in the army are looked at once a year by small arms personal (I am not talking about armors either) at a minimum they ensure barrels are straight, barrels are not shot out and everything is correctly headspaced. Tolerances for weapons overseas is tighter than those that are stateside. Meaning barrels stateside are allowed more erosion and are retained in use longer before being replaced.

Link Posted: 10/24/2004 10:01:51 AM EDT

The passage you refer to, as I have referenced earlier is found in the TM's and the TB's since the '70's. So it has been there in one form or another for years. I know that some of the information in the various SOUM, MAM, MWO's or bulletins for that matter don't always make it into the TM's. Though if you know where to look, you can usually find a copy of any of them, or a reference to them. I have researched this extensively and as of yet have not found a message to support any of these theories relating to chromed carriers/bolts accelerating wear or causing malfunctions.

Not trying to be a smart ass so please don't take it as such, but have you read all the post on this thread? Yes I know I have a habit of getting long winded in some of my replies. FWIW, I started out in the Marine Corps, 2111(Small Arms Repairman), in a DS/GS shop. Got into the Mil-Tech(Full time civilian part time reservist, been deployed to boot) program of the Army Reserves as a 45B(Small Arms Repairman) also at the DS level. Currently a CW3 913A(Armament Repair Technician) who is currently at the MMC level though I continue to get my hands dirty whenever I can. So yeah, I think I've figured out how the maintenance system works in the last 20+ years. And I do appreciate your input.

Wpns Man
Link Posted: 10/25/2004 4:05:52 PM EDT

Originally Posted By shamayim:

Originally Posted By rlc:
FWIW, i have a HC in a m16, and a cut unit in my competition ar, neither has ever shown signs of
flaking etc, i also have an ar-18, with a chrome bolt, many many rounds thru both the ar18 and m16, (to the point of melting a shortie gas tube once) and never a problem with the carrier
i am glad to see wpnsman set this straight....

Hmmmmm. Then maybe you can explain the early GI carrier key in my parts box, with significant wear on the chrome plating, down to the bare metal, on the sides.. As I recall, the carrier I pulled it off of also was showing signs of chrome loss at the edges of the bearing surfaces.

Sure do wonder where that worn off chrome went

did you inspect the upper that the carrier and key came out of?
was it damaged/unserviceable because of the chrome?
how about the charging handle?
was it wear from usage, or was the chrome flaking off in peices?
just for the heck of it i just pulled both carriers out of my ar and m16
both show "polishing" on the bearing surfaces and very little on the keys
neither upper show any signs of galling or excessive wear,
both rifles have in excess of 7-8000 rounds thru them, probably more, i don't count like i should
i have also noticed some polishing inside the carrier where the gas rings rub , but no flaking
i wore out a set of gas rings in a season shooting heavy (warm) loads in highpower, with no effect on functioning, (stainless rings inside a chrome carrier with hot gas)
my point is we are talking about a machine with moving parts that is going to have some wear and tear, having a chrome this or that (including barrel) is not going to prevent that, just delay it hopefully!
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